Combined voltage‐clamp and dialysis of Myxicola axons: behaviour of membrane asymmetry currents.

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Abstract
A new technique for the simultaneous internal dialysis and voltage-clamp of Myxicola axons is described and shown to control the internal composition of the axon adequately. The permeability ratio (PNa/PK) of the Na channel is 15.5 in axons dialyzed with Na-free solutions, somewhat higher than observed in perfused axons. Asymmetry currents are easily recorded in dialyzed Myxicola axons. At 4.degree.-5.degree. C for pulse durations sufficiently short Qon = Qoff with a maximum charge displacement of 10 nC/cm2 and half the charge being displaced by a step to -32 mV. Maximum slope of the Q(V) curve is 15 mV/e-fold change in charge displaced. The time .tau.on reaches a maximum of 325 .mu.s at a potential of -23 mV. The time course of Na activation cannot be adequately accounted for by (Q/Q.infin.).chi. using any single value of .chi. for potentials between -40 and 40 mV. Both asymmetry currents and INa are inactivated by the same amounts when Myxicola axons are repetitively depolarized at frequencies from 0.1-50 Hz.